Electrical insulator



Jan; 3, 1928.

E; A. DEAN ELECTRICAL INSULATOR Filed Sept. 28, 1923 E El,

Patented Jan. 3, 1928.'

UNITED STATES PATENT OFFICE.

EMMET ALPHA DEAN, OF OAK PARK, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ELECTRICAL INsULA'roR.

Application filed September 28, 1923. Serial No. 665,269.

This invention relates to electrical insulators, and more particularly to insulators employed with electrical currents of high voltages. l

Where insulators are used to insulate conductors carrying, or which may be subjected to, electrical currents of high voltages, it is desirable that the insulation afforded thereby be reliable under all operating conditions in order to properly protect, the associated apparatus and the operators attending the` apparatus. Any moisture which may collect on the electrical insulating material, such as by condensation from the r Surrounding atmosphere, vmay provide a leakage path for the electrical current present in the conductors associated therewith, which path may in some instances, especially when high voltage currents are employed,

materially lessen the insulation resistance of the insulator. Sometimes `due to a reduction in the temperature of the surrounding atmosphere moisture condenses therefrom upon the surface of the insulator, which deleteriously affects the insulating quality of the insulator. l y

Although it is desirable to maintain unimpaired the dielectric strength` of the electrical insulator, in all cases it is of'especial importance in connection with high voltage transmission lines, and high voltage oir-f cuits for testing the insulation resistance and capacitance of electrical apparatus. l

An object of the invention is yto maintain unimpaired the efficiency of anU insulator during a reduction inftemperature. f

Another object is to prevent the formation of leakage paths on the exposed surface of an electrical insulator.

A further objectistoshroud a body of electrical. insulating material with a heat conduction material, such as metal, which will tend to condense the moisture in a humid atmosphere.

An-electrical insulator ymade in accordance with one embodiment of the invention may comprise a body of insulating material, such as hard rubber, surrounding or otherwise supporting an electrical conductor, and which in turn `may be surrounded by a spaced shrouding member of metal, such as brass.

These and other features of the invention not specifically mentioned will clearly ap' lpear from the following description and the accompanying drawings, in which Fig. 1 shows a longitudinal View, in section, of an electrical insulator surrounding the conductor and associated with a. clamp type of mounting; CU Fig. 2 is a transverse section taken* along the lines 2-2 of Fig. 1; y

Fig. 3 is an elevation, partially in section, i of a modified form of the insulator shown in Figs. 1 and 2.

Referring t0 the drawings, in which similar reference characters are employed to denote similar parts throughout the various figures, a rod 10, of copper or other material suitable for the conduction of electrical current is surrounded by an insulating tube-'11, preferably of hard rubber. Tube 11 may be Iattached to the rod 10 by means-of a pin 12, the ends of which may be covered by any suitable insulating compound.' How- 75 ever, this method of attachment is not es- -to clamp Ytherebetween electrical terminals J 16, which maybe connected by. leads 18 and 19 to an electrical circuit (not shown) so 'that current may flow over'oiie of the leads through the conducting rod 10 and return over the other lead.

A metal sheath 20, preferably of brass, surrounds the tube 11 but is slightly shorter than` the tube and is attached thereto by means of -a screw 21'. The exteriordiaineter of the tube 11v is reducedfnear its ends 'to im provide' an annular-'space between the tube and the shrouding slieath'20. Cap oi'"pet'ti coat members 23 and 24 are'loosely 'nioui'ited upon the ends of the rod 10, being secured in position between the ends of the tube 11 es and the associated nuts 15, and having walls extending inwardly beyond the ends of the sheath 20. The assembled insulator may be mounted in a vertical or horizontal position upon a metal member 27, which although only (partially shown, may be suitably ati tache in any manner desired to a support. A clamping member 26, together with lbolts 28 and nuts 29 cooperate to secure the insulator in place upon the `(member 27. Howis mounted in a vertical position, it may be desirable to add a petticoat 30, preferably ofl rubber, which covers and prevents the entrance of foreign matter into the open end of the cap member 24 as shown in F ig.

It is Well known that a good conductor of heat, such as brass or other metal, responds more quickly and accurately to changes in temperatures than a poor conductor of heat, such as hard rubber. Therefore, when brass and hard rubber articles are placed closely ,adjacent to each other so as to be simultane- -ously subjected to a reduction in temperature, the moisture which may be condensed from the surrounding atmosphere will collect upon the relatively cool brass article, while the surface of the realtively warmer rubber article will remain substantially free from moisture. These characteristics of the dissimilar materials are employed in the present invention to maintain the insulative qualities of an electrical body unimpaired when exposed to humidity laden atmosphere and subjected to changing temperatures. l/Vhen the temperature of the atmosphere in which the insulator may be placed begins to fall, the brass shrouding member 9.0 cools more quickly than the associated enclosed hard rubber insulating body 11. Hence, the moisture which is condensed from the atmosphere, due to the lowering of the temperature, collects on the wall of the metal member, and since the relative temperatures of the metal and the rubber are maintained during further decreases in temperature, it is evident that the surface of the insulating body is maintained free from condensation at all times.

Vhat is claimedis:

1. An insulating support for an electric conductor requiring a high insulation resistance, consisting of an insulating tube having a central sect-ion of larger diameter than the end sections, a conductor passing through the center of the tube, a metallic sheath slightly shorter than the tube surrounding the tube but spaced therefrom a distance insuring the collection upon the interior surface of substantially all moisture condensed from the atmosphere between the exposed portion of the tube and the interior surface of the sheath, said sheath contacting with the central portion of the tube, a cap covering the end of the sheath in contact with the tube and the conductor but spaced from the sheath, and means for attaching an external conductor to the conductor leading through and supported by the tube.

2. In an electrical insulator, a tube of insulating material having a reduced end portion, an electric conductor surrounded by the tube, a metal sheath attached to and surrounding the tube and having its interior surface parallel to but spaced from the eX- terior surface of the reduced portion of the 'tube by a .distance insuring the collection upon the interior surface of substantially all moisture condensed from the atmosphere between the exposed portion of the tube and the interior surface of the sheath, and a cap covering the end of the sheath in contact with the reduced end of the tube and the conductor but spaced from the sheath.

In an electrical insulator, a metal rod, a rubber tube attached to and surrounding the rod, a metal sleeve attached to and surrounding the rubber tube, the end portions of the tube extending beyond the ends of the sheath and reduced in exterior diameter for a predetermined distance within the sh ath to provide access of atmosphere to the eX- terior surfaces of such portions and to portions of the interior surface of the sheath therearound, said portions of the interior surface being spaced from the surrounded exterior surfaces of the reduced portions by a distance insuring the selective collection thereon of substantially all of the moisture condensed from the atmosphere between said interior surface and the surrounded exterior surfacesof the reduced portions of the tube, metal caps for surrounding the ends of the sheath, means for securing the caps to and connecting electrical terminals with the rod, and a cap member of insulating material secured to the metal sheath and covering the open end of the lower metal cap.

In witness whereof, I hereunto subscribe my name this 18th day of September A. 1)., 1923.

EMMET ALPHA DEAN. 

